1. Field of the Invention
The present invention relates to a novel compatibilizing agent capable of compatibilizing a radical copolymerizable unsaturated resin with an addition polymerized polymer which is added exclusively for purposes such as low profile and improvement of physical properties, a radical copolymerizable unsaturated resin composition, a molding material, and a molded article. More particularly, the present invention provides a compatibilizing agent which remarkably improves the compatibility between two components, i.e. a radical copolymerizable unsaturated resin (e.g. an unsaturated polyester, a vinyl ester resin and a vinyl urethane resin) and an addition polymerized polymer comprising a thermoplastic resin (e.g. polystyrene, poly(methyl methacrylate), a styrene butadiene rubber, polyvinyl acetate and an acrylic rubber), and which is very useful for solving problems of preservation and molding caused by poor compatibility. Furthermore, the present invention prevents these resin mixtures from separating, and makes it possible to convert the resin mixture into a stable dispersion state, that is, a homogenous resin mixture free from separation. The present invention, because of the above effects, provides a compatibilizing agent which makes it possible to attain a high value-added product, radical copolymerizable unsaturated resin composition, a molding material, and a molded article.
2. Description of the Related Art
Radical copolymerizable unsaturated resins are suitably used as raw resins for molding materials. However, molding materials using the radical copolymerizable unsaturated resin have a large problem in which volume reduction, which occurs on curing, causes warpage and cracks in the molded article. To overcome the problem, various thermoplastic resins, for example, low profile additives such as polystyrene, styrene-butadiene rubber and the like are used. However, since these low profile additives have poor compatibility with the radical copolymerizable unsaturated resin and separation after mixing is unavoidable, the resin mixture does not convert well into a homogeneous resin mixture free from separation because of its poor separation stability. In addition, in a molded article obtained from the above resin mixture, various defects in the appearance of the molded articles, such as scumming and segregation caused by separation of a low profile additive, often occur.
Thus, various methods of adding a stabilizer as a third component have been investigated. For example, U.S. Pat. No. 3,836,600 discloses an example where a styrene-ethylene oxide block copolymer prepared by a living anion polymerization method is used as the stabilizer. This stabilizer exerts a high compatibilizing effect and can maintain a stable dispersion state for a long period of time. However, it was difficult to mass produce the stabilizer industrially because-of its special synthesis procedure.
On the other hand, a method of improving the compatibility by a procedure using an addition polymerized polymer introducing a vinyl acetate block, a saturated polyester block and the like into a low profile additive has been investigated (e.g., Japanese Unexamined Patent Application, First Publication No. Hei 3-174424 and Japanese Unexamined Patent Application, First Publication No. Hei 11-92646). These improved low profile additives have the effect of retarding the time required to separate, but a stable dispersion state is still to be obtained by essentially improving the compatibility. In addition, the above technology is limited to polymers having a particular structure, and therefore convenience of suitably selecting and using various types of addition polymerized polymer as a low profile additive depending on required physical properties, usage and the like, cannot be provided.
U.S. Pat. No. 3,947,422 provides a copolymer of styrene and half ester maleate of polyethylene glycol as a viscosity reducing agent which is added to a molding material, such as SMC and BMC obtained by using a vinyl ester resin. However, on converting into SMC, the remaining carboxyl groups from maleic acid, are absorbed to a filler such as calcium carbonate, and therefore the excellent compatibilizing effects for the purpose of the present invention can not be obtained. In addition, by an experiment in a system consisting of only unsaturated polyester and polystyrene without any filler, the present inventors have confirmed that there are some cases of exhibiting no compatibilizing effect. Therefore, conversion of many types of unsaturated resin and an addition polymerized polymer into a homogeneous resin mixture which is free from separation and scumming, uniform coloring properties, surface smoothness, gloss, and the like, of a molded article cannot be expected, while these are expected as effects of the present invention.
An object of the present invention is directed to essentially improve the compatibility between a radical copolymerizable unsaturated resin and an addition polymerized polymer (thermoplastic resin) which is added for the purpose of low profile and improvement of physical properties. Also an object of the present invention is to provide a compatibilizing agent which prevents molding defects caused by separation of the second component during the molding, or exhibit a stable dispersion state for a long period of time in the state of a resin mixed solution. That is, an object of the present invention is to provide a practical compatibilizing agent which makes it possible to convert the resin mixture into a homogeneous resin mixture free from separation and to eliminate defects (scumming, uniform coloring properties, surface smoothness and gloss) caused by separation during the molding by prevention of the separation between the radical copolymerizable unsaturated resin and addition polymerized polymer, which could not have been attained by the prior art, a radical copolymerizable unsaturated resin composition containing the same, a molding material, and a molded article.
The present inventors have intensively studied about these objects and found that a graft copolymer having a specific structure is very useful for the above compatibilizing agent, thus completing the present invention.
The present invention provides a compatibilizing agent for compatibilizing a radical copolymerizable unsaturated resin with an addition polymerized polymer, characterized in that said compatibilizing agent is a graft copolymer (A) which contains a styrene monomer as a principal component, and has a principal chain (A1) consisting of a copolymer with a (meth)acrylate monomer and a side chain (A2) selected from a ring-opening polymerized polyether side chain consisting of a polyoxyalkylene ether, a polyester side chain, and a polycarbonate side chain, the side chain (A2) being bonded to the principal chain (A1).
In the present invention, it is preferable to use a styrene monomer as a principal component which constitutes a principal chain (A1) of the graft copolymer (A) because of its excellent compatibilizing stability. In addition, the polyoxyalkylene ether, which constitutes a side chain (A2) in (A), is preferably a polyether containing oxyethylene units as a principal component. It is preferable in view of performance and synthesis that the number-average molecular weight is within a range 1,000-20,000, and more preferably 2,000-10,000. The present invention preferably provides a very useful radical copolymerizable unsaturated resin composition characterized in that: it comprises a compatibilizing agent, a radical copolymerizable unsaturated resin, an addition polymerized polymer and a polymerizable unsaturated monomer, the weight ratio (A1)/(A2) of the principal chain (A1) to the side chain (A2) in the graft copolymer (A) being preferably within a range of 90/10-20/80, and more preferably 80/20-20/80 (% by weight), the graft copolymer (A) being obtained by addition polymerization of an unsaturated monomer containing a styrene monomer which constitutes a principal chain (A1) as a principal component, and a macromonomer which constitutes a side chain (A2) and has a (meth)acrylic residue or styryl residue at one terminal; a molding material containing the radical copolymerizable unsaturated resin composition; and a molded article thereof.
According to the present invention, there can be obtained a practical compatibilizing agent which makes it possible to convert the resin mixture into a homogeneous resin mixture free from separation and to eliminate defects caused by separation during the molding by prevention of the separation between the radical copolymerizable unsaturated resin, and low profile additive (addition polymerized polymer) which could not have been attained by the prior art. Thus, the resin composition obtained by the compatibilizing agent of the present invention cases no separation of the low profile additive. The molding material has an excellent uniformity, therefore makes it possible to obtain a molded article having a very high quality, which is free from scumming and has excellent uniform coloring properties, surface smoothness surface gloss and the like.